An antibody against simatetro is disclosed, as well as a method for preparing it. The method is simple and cost-effective. The antibody assay has a detection range of 0.10 to 8.10 μg/L, a sensitivity of 0.51 μg/L, a detection limit of 0.10 μg/L, and a recovery rate of 80.81% to 127.80%. The antibody assay has low detection limits, high sensitivity, good stability, low cost, and high speed, making it suitable for trace analysis and batch testing of large sample sets.